WASHINGTON - Three weeks after a massive power blackout disabled much of Ohio, Michigan, New York, and Ontario, Energy Secretary Spencer Abraham said he still does not know what caused it and that for all he knows, it could happen again. In eight hours of hearings that did not pause for lunch and will continue today, the House Energy and Commerce Committee had lots of questions but got few answers.

WASHINGTON - Three weeks after a massive power blackout disabled much of Ohio, Michigan, New York, and Ontario, Energy Secretary Spencer Abraham said he still does not know what caused it and that for all he knows, it could happen again.

In eight hours of hearings that did not pause for lunch and will continue today, the House Energy and Commerce Committee had lots of questions but got few answers.

The panel heard from a parade of government experts, industry analysts, and governors who professed themselves still in the dark about why the great blackout of 2003 occurred.

It affected 50 million people, caused billions of dollars in damage and lost productivity, and involved 34,000 miles of transmission lines and 100 power plants, despite the belief that such a widespread outage couldn't happen.

As expected, Mr. Abraham and Republicans on the committee clamored for immediate action on President Bush's energy bill, which passed the House 247-175.

The Senate has passed a different bill, and a conference committee must reconcile them.

But while some Democrats voted for the House bill, which unlike the Senate includes permission to drill for oil and gas in the Arctic National Wildlife Refuge in Alaska, Democrats overwhelmingly oppose the House bill. Instead they demanded passage of a bill that would require the industry to adopt so-called reliability standards.

But there is no overall authority with the power to enforce the standards, and the group can't set penalties.

Although investigators are still looking at whether the blackout began with problems within the FirstEnergy Corp. system in Ohio, there was no speculation about the company nor any mention of its recent troubles during the hearing.

Democrats want a combination of state and federal controls. Republicans have agreed to that provision but want it attached to the overall energy bill.

In addition to the oil and gas-drilling provision, many Democrats oppose the energy bill, claiming it is too favorable to industry.

Rep. Ed Markey (D, Mass.) said that passing the energy bill without knowing the cause of the blackout would be like having a doctor say he didn't know why the patient had blacked out but that he would perform brain surgery in the morning.

Environmental groups claim that nothing in the energy bill would improve the reliability of the interstate power grid anytime soon. Environmentalists want more emphasis put on energy conservation, not more production.

Mr. Abraham, who was out of the country when the blackout struck, said the task force formed with Canada to find out why it happened should have an answer in a matter of “weeks, not months.”

But Mr. Gent said that while his group has 90 percent of the data needed for its own investigation, his report won't be final for a year.

The scope of the devastation caused by the blackout is just becoming clear.

Michigan Gov. Jennifer Granholm said that in her state 6 million people lost power, 70 plants had to close, and that the state had at least $1 billion in lost earnings.

While she said “we need to wait for the investigations to be completed before we jump to conclusions,” Ms. Granholm said she believes human errors and communication failures were a factor because there were no courtesy calls for 65 minutes after surges of power were reported.

Unlike water, electricity cannot be stored but travels at the speed of light and has to go somewhere.

While failsafe measures are supposed to shut vulnerable lines off from damaging surges, somehow they didn't all work on Aug. 14.

Ms. Granholm said another potential cause for the blackout was power-line failure, possibly a result of inadequate maintenance.

Another factor she cited, but which is strenuously disputed by many, is deregulation of the power industry, which has resulted in power companies selling off transmission systems to separate operators, which operate on a supply-and-demand basis.

Ohio Gov. Bob Taft said the cost to Ohio was about $1 billion because of interruptions in business, including one plant which, he said, lost steel-making capacity for more than a week.

“Above all, the blackout shook the confidence of our citizens in a system that most take for granted,'' he said.

He said voluntary standards to keep electricity flow reliable have failed and that the industry needs mandatory standards along the lines of rail lines and natural gas pipelines, whereby the states enforce national safety and reliability standards.

He said he also wants the Federal Energy Regulatory Commission to set up a regional system that puts the direction and control of transmission with independent regional grid operators.

In Ohio, he said, two different groups have oversight of transmission lines, resulting in ineffective control.

Like Ms. Granholm, Mr. Taft said that in the 21st century, a system that relies on “courtesy calls” to alert others to problems on the lines is “clearly outdated and must be modernized.”